For CA emissions the muffler shouldn't matter. As long as the vehicle has all the smog equipment on it as it came from the factory (and in working order) you should pass. 49-state vehicles only need to pass 49-state emissions, 50-state vehicles need to pass CA emissions. If the vehicle is 49-state you'll probably have to fork out some extra money as a smog abatement fee and show prior residency and proof of registration for the state you are moving from.